Automatic elevator car systems, i.e., systems in which the car door automatically opens when the car reaches a landing floor and closes before the car leaves a landing floor, are well-known in the art. Conventional elevator systems also may have either an automatic sliding or a manually operable, swinging hoistway door. In such systems, the hoistway door may be automatically opened and closed or may be manually opened and closed. In such systems, there usually is a switch or switches operable when the hoistway door is closed and a switch or switches operable when the car door or gate is closed which permits the car hoisting system to move the car to another landing floor when all switches have been operated to obtain a predetermined switching state, such as closed. Also, such systems usually include locking assemblies which prevent opening of the doors unless the car is substantially level with the floor at which the doors control entrance and egress from the car, and include an edge detector on one or more of the doors to reopen the doors and prevent starting of a car from a floor when closing of a door is obstructed.
Various locking assemblies are available that operate to unlock and open an elevator car door only when the locking assembly engages with a corresponding engagement assembly on a hoistway door. In such assemblies, the unlocking and opening of the elevator car through the engagement of the locking assembly with the engagement assembly can occur only when the elevator car arrives at or near a landing floor. If the elevator car stops between floors, the locking assembly under normal operation prevents unlocking and opening of the elevator car, as engagement with the corresponding engagement assembly on a hoistway door does not occur.
There are occasions when movement of an elevator car stops for various reasons, e.g., a power or control failure etc. If the car stops close to a landing floor where a passenger may exit from the car, there is no objection to permitting a passenger to force the car doors open manually since the hoistway doors may be opened, or are open, and the passenger may exit safely. However, if the floor of the car is a substantial distance from level with the landing floor, a passenger, while exiting from the car, may fall under the car into the hoistway.
Although a separate door position detection assembly may be used in conjunction with a locking assembly to detect whether the locking assembly is an unlocked or locked state and provide information, via electronic means, indicating the locking state, and thus whether the elevator car is opened or closed, to an elevator control unit, such detection assembly is an additional component adding cost and complexity to components used to operate elevator car doors and hoistway doors of an elevator system. In addition, when the door position detection assembly and the locking assembly operate independently from one another, there is a risk that one may be disabled without also disabling the other, causing a disconnect between the two assemblies.
There is a need for a simple and inexpensive elevator car locking system that is operable to unlock and lock an elevator car door based on the position of an elevator car door in relation to a hoistway door and to supply information indicating whether the locking system is in an unlocked or locked state, thereby indicating whether the elevator car door is open or closed.